Metal forming



Nov. 28, 1967 TlRONE 3,354,689

METAL FORMING Filed July 15, 1965 3 Sheets-Sheet 1 FIGI {M IA. HGIA INVENTOR ANTHONY R T IRONE Byozazxzb ATTORNEY A. R. TIRONE METAL FORMING Nov. 28, 1967 3 Sheets-Sheet Filed July 13, 1965 INVENTOR ANTHONY R. TIRONE BY /%z/ ATTORNEY Nov. 28, 1967 A. R. TIRONE 3,354,689

METAL FORMING Filed July 13, 1965 5 Sheets-Sheet 3 FIGIO A INVENTOR ANTHONY R. TIRONE ATTORNEY United States Patent of Delaware Filed July 13, 1965, Ser. No. 471,547 19 Claims. (Cl. 72-334) The present invention relates to improved processes for cold forming components from heavier gauges of standard steel rod or bar stock. It especially relates to making automobile suspension parts having configurations which differ substantially in size and shape from the starting material, yet must be structurally and functionally sound under varying load conditions.

Automotive suspension systems and the components thereof must be capable of meeting a variety of rather severe operating conditions, and functional requirements under widely differing conditions. These include, for example: wide range of speeds with varying force of impact, different road and oif-the-road conditions, space and weight limitations for below-chassis auto components, simplicity in design, etc. However, in addition to being structurally and functionally satisfactory, it is essential that auto suspension systems and components be produced at minimum costs with maximum reliability.

Accordingly, for many years leading auto companies and their component suppliers have been continuously engaged in design and development of new suspensions systems and components, and new, improved methods and apparatus for making the same.

In the past few years a new type of automotive suspension system has been developed including some components produced from round rod up to one inch (1") diameter. In making these parts, the starting material is usually wire stock of suitable diameter (e.g., one inch), but it could be bar stock. Typically, the basic rod diameter extends for a substantial portion of the length of the part, but an enlarged section is usually formed adjacent one end of the part to provide a land for attachment to the car frame or another intermediate component. Usually, the other end of the part is also provided with attachment means in the form of threads. The enlarged lands are formed from the round rod starting material by upsetting, coining, and punching, etc., to obtain the desired shape. In many cases the amount of material to be moved, and thus the degree of deformation, exceeds the limitations of known cold forming techniques, causing cracking, brittleness, decrease in transverse properties and other deterioration in mechanical properties which make the part unsatisfactory. When these conditions exist, the enlarged lands of suspensions parts made from round bar stock are usually formed by hot forging techniques. (For distinction between hot working and cold working and background on hot forging and cold forging, respectively, see Principles of Physical Metallurgy, by Doan and Mahla, McGraW-Hill, 2nd ed., pp. 128-134, and Practical Metallurgy, by Sachs and Van Horn, American Society for Metals, pp. 335-360.)

However, hot forging processes are more expensive than cold forging, thereby substantially increasing the cost of the part. Since there has been continuous pressure from the major auto companies to reduce cost, considerable time, eifort and money has been spent to develop cold forging techniques which would enable production of components having large sections from wire rod or bar stock by more economical cold forging processes. Also, hot worked products are generally inferior to cold worked products in various respects such as warpage, uniformity of structure and properties, surface conditions and dimensional tolerances, tensile strength and hardness.

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It is therefore the purpose of this invention to provide a novel, improved method for cold forging from rod or bar stock parts having enlarged lands of desired finished configuration and dimensions, without the application of heat. It is a related object of this invention to cold form auto suspension parts from steel rod or bar stock in a manner which increases tensile strength and hardness and otherwise improves physical properties.

It is also an object of this invention to provide an improved, substantially rod-type part having an enlarged portion which is formed by cold upsetting in a first operation to gather sufficient material and then coining to a final overall width and length dimensions in a second operation, after which further cold forging operations are performed to obtain the desired thickness configuration without increasing the length and width dimensions of the enlarged portion.

It is another related object to provide a novel process in which the operations for obtaining desired configuration and thickness comprise punching (or drilling) the part approximately at the center of the enlarged area after such gathering and coining, and then trapping the outer material of the enlarged portion against radially outward flow so that further compression operations cause the excess material of the enlarged portion to flow radially into the space provided by the punching (or drilling).

It is another object to provide a novel process comprising a unique sequence of metal forming operations producing an improved cold-forged product from rod or bar stock.

It is another related object to achieve economical production of such improved cold-forged auto suspension components from rod or bar stock so as to achieve important competitive advantages which are crucial in the highly competitive business of supplying components to automobile manufacturers.

Other objects and advantages will become apparent from the following description with reference to the drawings in which:

FIGURE 1 is a side view of the rod blank from which all further forming operations are performed, and FIG- URE 1A is a cross-sectional view thereof along line 1A- 1A in FIGURE 1;

FIGURE 2 and FIGURE 2A (cross section along line 2A2A in FIGURE 2) indicate the shape of the part after the first operation of upsetting has been accomplished;

FIGURE 3 shows the part after its enlarged portion has been coined to the final width configuration, and FIGURE 3A is a cross-sectional view along line 3A-3A in FIG- URE 3;

FIGURE 4 and FIGURE 4A (cross section along line 4A4A in FIGURE 4) show a hole punched approximately in the center of the enlarged area formed by the previous coining and upsetting operations;

FIGURE 5 shows the configuration of the part after a further coining or dimpling operation in which the material is caused to flow radially into the punched hole while the exterior of the enlarged portion is trapped and restrained against outward flow, and FIG'URE 5A is a cross-sectional view along line 5A5A in FIGURE 5;

FIGURE 6 indicates the finished part with attachment holes punched to size, and FIGURE 6A is across-sectional view along line 6A6A in FIGURE 6;

FIGURE 7 is a top plan View illustrating a suitable holder for trapping the exterior of the enlarged portion of the part shown in FIGURES 4 and 4A to dimple the same so that material flows radially inward producing an intermediate part as shown in FIGURES 5 and 5A.

FIGURE 8 is a side elevation view of the holder of FIGURE 7 (looking in the direction of arrows 88 in FIGURE 7).

FIGURE 9 is an end elevation view of the holder shown in FIGURES 7 and 8 (looking in the direction of arrows 99 in FIGURES 7 and 8).

FIGURES 10 and 10A, respectively, show side elevation and top plan views of a suitable dimpling tool for use with the holder of FIGURES 7-9.

In any metal forging process, the amount of material which can be displaced to achieve desired configuration is limited in a given operation to the amount of deformation the material can withstand without fracture. It has, therefore, been the practice to mechanically work metal by drawing, upsetting, coining and forging in stages which are within the range of deformation of the material so as to achieve a satisfactory product. This is especially important for cold forging of structural parts like auto suspension components from commercial grade steels for use under widely Varying and frequently severe loading conditions. The present invention provides an ingenious method whereby permissible maximum deformation of the material is not exceeded, as will now be fully described.

Referring to FIGURES 1 to 6A, the starting material, shown at 14, is wire rod or bar stock of suitable diameter. In the preferred embodiment, starting material 14 is commercial grade steel wire rod (e.g., 1022 steel, cold heading quality) which, after receipt from the steel mill, is drawn by known techniques in order to provide improved tensile strength, straighten the rod and obtain an outside diameter d of desired dimension (e.g., approximately %1 inch). (For background on drawing and straightening wire rod, see aforementioned Practical Metallurgy, pages 380-392.) The drawn rod 14 is then cut to suitable length for making the end product. In FIGURES 1 to 6A, the portion of rod 14 which is usually threaded is shown at the left of the drawing; and rod 14 is cut so that a portion (shown at the right of the drawings) initially extends beyond the subsequently formed enlarged land section 16, for reasons amplified below with particular reference to FIGURE 6.

Referring now especially to FIGURES 2 and 2A, rod 14 is upset to ball the rod 14 and increase the volume of metal at rod portion 16 from which the enlarged land is to be formed. (For background on upsetting, see aforementioned Practical Metallurgy, pages 348359.)

Referring now especially to FIGURES 3 and 3A, the rod 14 and bailed section 16 are coined to produce sections with flattened sides as shown at 16a, 14a and 14b. In thisoperation, sections 16a, 14a and 1411 are coined to the final width configuration and dimensions shown at W1 and d in FIGURE 3. The dimensions W1 and d produced by coining are to be within the deformation limits of the particular material used so that physical properties will be satisfactory and avoid brittleness, cracking or other deleterious effects, as will be clear to those skilled in the art in light of the disclosure herein. Also, this coining operation likewise reduces enlarged land section 16a and rod sections 14a and 14b to a suitable thickness t (per FIG'URE 3A).

Referring now especial-1y to FIGURES 4 and 4A, a hole 18 is punched (or drilled) through enlarged land section 16a and substantially at the center of the same, as shown in the drawings. The hole 18 should be of suflicient size to provide space for excess material to flow radially inwardly during the subsequent dimpling operation, which will now be described with particular reference to FIGURES 5, A, and 7 to A.

The part formed as shown in FIGURES 4 and 4A, in the manner described above, is placed in a suitable dimpling holder, generally indicated at 20 in FIGURES 7-9. Dimpling holder comprises two mating body sections 22 and 24, which can be secured together by any suitable means, such as cap screws 26 extending through apertures 28 in dimpling holder body section 22 and threaded into taped apertures 30 in body section 24. (For rapid mass production, dimpling holder 20 would generally be provided with a more sophisticated means for rapidly opening, closing and securing body sections 22 and 24.)

The internally disposed face of each of the body sections 22 and 24 of dimpling holder 20 is provided with a recessed portion including: sections 32 and 34 for receiving and holding sections of rod 14; sections 36 and 38 for receiving and holding coined sections 14a and 14b; and section 40' which receives the enlarged coined land section 16a with a relatively close fit to trap the material of land 16a so as to prevent radially outward flow of material during dimpling in holder 20 to produce the intermediate part shown in FIGURES 5 and 5A. In actual volume production, the center recessed portions 40 are provided with two small recessed areas shown at 42 in FIGURES 7, 8 and 9, to provide relief for expansion of metal during the dimpling operation to prevent die breakage in forming the part as shown in FIGURES 5 and 5A, in the event portion 16a of the predimpled part shown in FIGURES 4 and 4A should be slightly too large.

Each of body sections 22 and 24 of dimpling holder 20 is provided with aligned bores 44 and 46 (as shown in FIGURES 7, 8 and 9) to receive each of a pair of like dimpling plugs or tools comprising a main cylindrical section 49 and a beveled end 50, as shown at 48 in FIG- URES 10 and 10A, to which reference is made.

The partially formed part shown in FIGURES 4 and 4A is placed within dimpling holder 20; and dimpling tools 48 extending through aligned apertures 44 and 46 are forced towards each other. Since the material of on larged section 16a is restrained against radially outward flow by surrounding recess section 40 within die holder 20, the beveled ends 50 of tools 48 cause the material to flow radially inward during the dimpling operation, into the space provided by punched aperture 18. This results in a central section 17 of reduced thickness t surrounded on each side by an annular beveled section 19, with an irregularly shaped smaller central aperture 181:. (There may be a slight flash as shown at 21, by virtue of relief fiow of metal into relief recesses 42 of dimpling holder 20.)

Referring now especially to FIGURES 6 and 6A, subsequent punching and/or machining operations are performed as required to satisfy the design requirements for the finished product. An aperture 18b is punched or drilled to provide a sized hole for attachment of end 14b of suspension component 14 to part of the auto; and additional apertures 52 may be similarly provided for such purpose. Comparing FIGURES 5 and 6, rod section 14b is cut to provide a somewhat chisel-shaped end 54. It has been found preferable to cut this end 54 after completion of the above discussed operations, as this sequence appears to provide a better product; but, the sequence of operations in this regard can be modified while utilizing other novel aspects and advantages of this invention as discussed above.

It is noted that the relative proportions of starting rod 14 and cold formed portions thereof shown in FIG- URES l to 6A are representative for cold forging of -%1 inch rod by means of the present invention. By way of example, starting with 1022 cold heading quality steel wire rod 14 which has been initially drawn and straightened, having a diameter d of about 0.77 inch; ball 16 would be upset with a diameter of about 1.25 inches; land section 16a would be coined to a diameter :1 of about 1.58 inches, and a thickness 1 of about 0.44 inch, with coined r'od sections 14a and 14b having a width of about 1.08 inches; punched hole 18 would have a diameter of about inch; dimpled section 17 would have a thickness of about 0.15 inch; bevels 19 would have an inner diameter of about Ms inch and outer diameter of about 1 7 inches; irregular hole 18a would have an average diameter of about to 7 inch; and final aperture 18b would have a diameter of about inch.

It is noted that this invention enables maximum displacement and outward deformation of material of rod 14 in the upsetting and coining operation discussed with reference to FIGURES 2 and 3. If material of enlarged section 1611 per FIGURE 3 were allowed to stretch further radially outwardly in subsequent forming operation, that would exceed the deformation limit of the material and cause splitting or cracking of the material in such a cold forming operation. However, it has been found that although the formation of land 16a of FIG- URES 3 and 3A involves maximum deformation radially outward, it is possible thereafter to displace material substantially inward under compression when dimpling, while avoiding fracture of the material by restraining the peripheral portions of upset and coined land 16a against further outward displacement, as center hole 18 permits the deformed material to flow radially inward.

Using wire rod having a diameter of to 1 inch (after drawing from mill stock), automobile suspension components may be made by cold forging according to the present invention with deformations ranging as follows:

(a) Ratio of maximum deformation (radially outward elongation) of enlarged land diameter d to rod diameter d is approximately 2 to 1.

(b) Ratio of additional maximum deformation (radially inward compression) is: (l) with reference to outer diameter of dimpled annular bevel 19 cf. diameter 18a, approximately 3.7-4.6; and (2) with reference to predimpled hole diameter 18 cf. dimpled hole diameter 18a, approximately 2.02.S.

(c) Ratio of compression to final thickness t of dimpled portion 17 from thickness t of coined section 16a (and 14a and 14b) is up to approximately 1 to 3; and the ratio of compression final thickness t of dimpled portion 17 to starting rod diameter d is up to approximately 1 to 56.5.

It will be apparent from the foregoing that the present invention provides a novel, improved cold forging method and apparatus for making auto suspension components and like structural parts from commercial steel in an efficient manner producing an improved product at lower cost from wire rod or bar stock, and avoiding various shortcomings of hot forging process. It is also apparent that the present invention achieves various objectives and functional and competitive advantages discussed earlier in this application.

Definitions of terms in claims: (1) the term rod refers to wire rod or bar stock or like starting material, generally of circular or like cross'section; (2) the term steel refers to steels of suitable quality for processing according to this invention, and the above-mentioned 1022 cold heading steel is merely one example thereof; (3) the term punching an aperture or hole includes drilling or other equivalent means for forming an aperture in the work piece; (4) the term land refers to an enlarged section formed from a rod by working the same, and land 16a as shown is merely one example thereof.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A process for forming a component with an enlarged land from metal rod, comprising: upsetting a portion of the rod to provide an enlarged section thereof having an increased volume of metal; coining the rod in the region of said enlarged upset section to form an enlarged land of desired maximum diameter and of desired thickness; punching in said enlarged land an aperture of sufficient size to provide space for inward flow of excess metal in a subsequent dimpling operation; dimpling a portion of said enlarged land around said aperture punched in the land, thus reducing the dimpled part of the land to desired thickness and causing metal to fiow inwardly into the space created by the aforementioned aperture punched in said land; and punching the dimpled land portion of reduced thickness to remove metal surrounding said aperture resulting from dimpling and thus provide a hole of desired size and configuration.

2. A process for forming a component with an enlarged land from metal rod comprising: drawing mill stock rod to desired diameter; and thereafter upsetting, coining, punching, dimpling, and punching again after dimpling, as set forth in claim 1.

3. A process for forming a component with an enlarged land from metal rod as defined in claim 1, further comprising cutting ofi an end portion of said flattened land after said last-mentioned punching step, thus shaping the end of the land to desired size and configuration and removing any excess portion of metal rod extending from :said end of the land.

4. A process for forming a component with an enlarged land from metal rod as defined in claim 1, further comprising the steps of: drawing mill stock rod to desired diameter prior to said first upsetting step; and cutting the end portion of the flattened land after said last-mentioned punching step, thus shaping said end of the land to desired size and configuration and removing any excess portion of metal rod extending from said end of the land. 5. A process for forming a component with an enlarged land from metal rod as defined in claim 1 wherein: said enlarged land formed by coining has arcuate side portions with a maximum diameter of up to about two times greater than the diameter of the metal rod prior to upsetting.

6. A process for forming a component with an enlarged land from metal rod as defined in claim 5 wherein: the ratio of additional deformation radially inward due to said dimpling operation, measured by the relation of the size of the outer diameter of the dimpled portion of the land to the average diameter of the smaller aperture after dimpling, is approximately 3.7 to 4.6.

7. A process for forming a component with an enlarged land from metal rod as defined in claim 5 wherein: the ratio of additional deformation radially inward due to said dimpling operation, measured by the relation of the dimension of said aperture punched in said land prior to dimpling and the resultant smaller aperture after dimpling, is approximately 2.0 to 2.5.

8. A process for forming a structural component with an enlarged land from steel rod comprising: upsetting a portion of said steel rod to provide an enlarged section having an increased volume of metal; coining said steel rod in the region of said upset-enlarged section to form an enlarged land having arcuate side portions of desired over-all diameter and opposing surfaces of desired thickness; punching in said enlarged land an aperture of sufficient size to provide space for inward flow of excess material in a subsequent dimpling operation; restraining the outer periphery of said arcuate side portions of the enlarged coined land section so as to prevent outward flow of material, and dimpling opposite sides of part of said enlarged coined land substantially concentric with said aperture punched in the land, thus reducing this part of the land to desired thickness and causing metal to flow inwardly into the space created by said aperture punched in the land; and punching the dimpled land portion of reduced thickness to remove metal surrounding said aperture resulting from dimpling and thus provide a hole of desired size and configuration in said land; all of said operations being cold forming.

9. A process for forming a component with an enlarged land from steel rod comprising: drawing mill stock teel rod to desired diameter; and thereafter upsetting, :oining, punching, restraining and dimpling, and again )unching after dimpling as set forth in claim 8.

10. A process for forming a component with an enarged land from steel rod, as defined in claim 8, further :ompris'ing: cutting the end portion of the flattened land ifter said last-mentioned post-dimpling punching step, thus ahaping the end of the land to desired size and configuraion and removing any excess portion of the steel rod :tarting material extending from said end of the land.

11. A process for forming a component with an enarged land from steel rod, as defined in claim 8, further :omprising: drawing mill stock rod to desired diameter prior to said upsetting step; and cutting off the end por- ;ion of the flattened land after said post-dimpling punch- .ng step, thus shaping the end of the land to desired size and configuration and removing any excess portion of steel rod starting material extending from said end of :he land.

12. A process for forming a component with an enlarged land from steel rod, as defined in claim 8, and wherein the aforesaid arcuate side portions of said enlarged coined land have a maximum diameter of up to about two times as large as the diameter of the steel rod prior to upsetting.

13. A method as defined in claim 12 wherein the ratio of additional deformation radially towards the center of said punched aperture due to said dimpling step, measured by the relation of the size of the outer diameter of the dimpled land portion of reduced thickness to the average diameter of the resultant smaller aperture after dimpling, is up to approximately 3.7 to 4.6.

14. A process for forming a component with an en larged land from steel 1 d as defined in claim 12, wherein the ratio of additional deformation radially towards the center of said punched aperture, due to said dimpling operation, measured by the relation to the dimension of said aperture punched in the land prior to dimpling and the average diameter of the resultant smaller aperture after dimpling, is up to approximately 2.0 to 2.5.

15. A process for forming a component with an enlarged land from steel rod as defined in claim 12, wherein the ratio of the thickness of the aforesaid coined land section to the final thickness of the compressed land portion formed by dimpling is up to approximately 3 to 1.

16. A process for forming a component with an enlarged land from steel rod as defined in claim 12, wherein the ratio of the starting rod diameter to the final thickness of the compressed portion formed by dimpling is up to approximately 5-6.5 to 1.

17. A process for forming an auto suspension component with an enlarged land from steel rod, comprising: drawing mill stock steel rod to desired diameter; upsetting a portion of said steel rod to provide an enlarged section having an increased volume of metal; coining said steel rod in the region of said enlarged upset section to form an enlarged land having arcuate side portions of desired overall diameter and opposing surfaces of desired thickness, said arcuate side portions of the coined land having a maximum diameter of up to about two times as large as the diameter of the drawn steel rod; punching an aperture in said enlarged land substantially concentric with the center of said arcuate side portions of the land, with said aperture being of sufficient size to provide space for inward flow of excess material in a subsequent dimpling operation; restraining the outer periphery of said arcuate side portions of the enlarged coined land section so as to prevent outward flow of material, and dimpling opposite sides of a portion of said enlarged coined land substantially concentric with said aperture punched in the land, thus reducing this part of the land to desired smaller thickness and causing metal to flow inwardly into the space created by said aperture punched in the land; and punching the dimpled land portion of reduced thickness to remove metal surrounding said aperture resulting from dimpling and thus provide a hole of desired size and configuration in said land; and cutting the end portion of the flattened land after said last-mentioned post-dimpling punching step, thus shaping the end of the land to desired size and configuration and removing any excess portion of the steel rod starting material extending from the end of said land; all of said operations being cold forming.

18. An apparatus for forming a component with an enlarged land from metal rod, a portion of which has been upset to provide an enlarged section with increased volume of metal, and thereafter coined on opposite sides in the region of said enlarged upset section to form an enlarged land having arcuate side portions of desired over-all diameter and substantially fiat opposed surfaces of desired thickness, and thereafter punched to provide in said enlarged coined land an aperture of sufficient size to provide space for inward flow of excess metal in a subsequent forming operation, said apparatus comprising: a holder including two body sections; each of said body sections having mating recesses in one face thereof; each of said mating recesses including a first section for receiving and closely surrounding the outer periphery of said arcuate side portions of the enlarged coined land section thereby restricting outward flow of material therefrom, with second recess sections extending from each side of said first recess section for receiving coined rod portions extending from opposite sides of the arcuate enlarged coined land portion and third recess sections for receiving portions of said metal rod of same diameter as prior to upsetting; means for clamping said body sections together; and aligned apertures, one in each of said body sections, for receiving a tool, each of said apertures having its longitudinal axis extending perpendicular to the longitudinal axis of the aforementioned mating recesses in the face of each of said body sections.

19. An apparatus as defined in claim 18, further comprising a dimpling tool within each of said last-mentioned apertures in each body section of holder.

References Cited UNITED STATES PATENTS RICHARD J. HERBST, Primary Examiner. 

1. A PROCESS FOR FORMING A COMPONENT WITH AN ENLARGED LAND FROM METAL ROD, COMPRISING: UPSETTING A PORTION OF THE ROD TO PROVIDE AN ENLARGED SECTION THEREOF HAVING AN INCREASED VOLUME OF METAL; COINING THE ROD IN THE REGION OF SAID ENLARGED UPSET SECTION TO FORM AN ENLARGED LAND OF DESIRED MAXIMUM DIAMETER AND OF DESIRED THICKNESS; PUNCHING IN SAID ENLARGED LAND AN APERTURE OF SUFFICIENT SIZE TO PROVIDE SPACE FOR INWARD FLOW OF EXCESS METAL IN A SUBSEQUENT DIMPLING OPERATION; DIMPLING A PORTION OF SAID ENLARGED LAND AROUND SAID APERTURE PUNCHED IN THE LAND, THUS REDUCING THE DIMPLED PART OF THE LAND TO DESIRED THICKNESS AND CAUSING METAL TO FLOW INWARDLY INTO THE SPACE CREATED BY THE AFOREMENTIONED APERTURE PUNCHED IN SAID LAND; THE PUNCHING THE DIMPLED LAND PORTION OF REDUCED THICKNESS TO REMOVE METAL SURROUNDING SAID APERTURE RESULTING FROM DIMPLING AND THUS PROVIDE A HOLE OF DESIRED SIZE AND CONFIGURATION. 